An optical transport hierarchy (OTH) technology is a new generation standardized digital transport hierarchy structure, which is used to transport a payload on which corresponding adaptation is performed on an optical fiber transmission network. An optical transport network (OTN) based on the OTH is a transparent transport technology developed and formed for high-capacity and coarse granule scheduling requirements of a backbone network hierarchy, and the OTN adopts a digital envelope technology. The OTN provides a new generation optical transport platform which is manageable, operable and highly efficient for network operators and clients.
FIG. 1 shows a multiplexing and mapping relation of OTN signals defined in the ITU-T G.709. As shown in FIG. 1, the name of each unit in FIG. 1 is as follows: an optical channel payload unit (OPU), an optical channel data unit (ODU), an optical channel transport unit (OTU), and an optical channel data tributary unit group (ODTUG).
It can be seen from FIG. 1 that multiplexing and mapping of OTN signals mainly include following six situations:
1. client signal (such as Synchronous Transfer Mode (STM)-16)->OPU1->ODU1->OTU1
2. client signal (such as STM-64)->OPU2->ODU2->OTU2
3. client signal (such as STM-256)->OPU3->ODU3->OTU3
4. client signal*4 (such as STM-16)->OPU1*4->ODU1*4->ODTUG2->OPU2->ODU2->OTU2
5. client signal*16 (such as STM-16)->OPU1*16->ODU1*16->ODTUG3->OPU3->ODU3->OTU3
6. client signal*4 (such as STM-64)->OPU2*4->ODU2*4->ODTUG3->OPU3->ODU3->OTU3
When a path is established through generalized multi-protocol label switching (GMPLS) signaling, how an ODUk is multiplexed into an ODUj (j>k) must be specified. For example, in Situation 4, the ODU2 has four tributary slots (TSs) and the signaling has to specify which one of the four TSs of the ODU2 signal of the ODU1 is mapped to.
RFC4328 describes signaling extension for the OTN defined by the ITU-T G.709 and describes label definition of the OTN. This label definition is able to indicate how the ODUk is multiplexed into the ODUj (j>k).
A label defined by the RFC4328 is as shown in FIG. 1a: 
t1:
t1=1, which indicates that it is an ODU1 signal; and
t1=0, which indicates that it is not an ODU1 signal.
t2:
t2=1, which indicates that it is an ODU2 signal; and
t2=2, 3, 4, 5, which indicates that an ODU1 signal is mapped to a certain one of four TSs of an ODTUG2, for example, t2=2 corresponds to a first TS, t2=3 corresponds to a second TS, and so on. The ODTUG2 is then mapped to the ODU2, and then mapped to the OTU2.
t2=0, which indicates that it is not the ODU1 or ODU2 signal.
t3:
t3=1, which indicates that it is an ODU3 signal; and
t3=2, 3, . . . , 17, which indicates that the ODU1 signal is mapped to a certain one of sixteen TSs of the ODTUG3, for example, t3=2 corresponds to a first TS, t3=3 corresponds to a second TS, and so on. The ODTUG3 is then mapped to the ODU3, and then mapped to the OTU3.
t3=18, 19, . . . , 33, which indicates that the ODU2 signal is mapped to a certain one of sixteen TSs of the ODTUG3. As four TSs need to be occupied when the ODU2 is multiplexed to the ODU3, in this case, four labels are needed to indicate which four TSs of the ODTUG3 are occupied by the ODU2 respectively.
For example, an ODU2 is multiplexed into an ODU3. If four parts of the ODU2 are mapped to a first, fifth, sixth, and ninth TS of the ODTUG3 respectively, the following four labels are needed.
A first label: t3=18, t2=0, and t1=0, which indicates that a first part of the ODU2 is mapped to the first TS of the ODTUG3.
A second label: t3=22, t2=0, and t1=0, which indicates that a second part of the ODU2 is mapped to the fifth TS of the ODTUG3.
A third label: t3=23, t2=0, and t1=0, which indicates that a third part of the ODU2 is mapped to the sixth TS of the ODTUG3.
A fourth label: t3=26, t2=0, and t1=0, which indicates that a fourth part of the ODU2 is mapped to the ninth TS of the ODTUG3.
In an innovating process of the present invention, the inventor finds that the prior art at least has the following disadvantages:
When an ODUk signal is multiplexed to an ODUj (k<j) signal, in most cases, multiple labels are required to specify each multiplexed TS. For example, when an ODU2 signal needs to be multiplexed to an ODU3, four labels (4*32 bit) need to be carried in a label request of the signaling, which specify which four TSs are multiplexed to the ODU3. Furthermore, if a label definition thought of the RFC4328 is adopted to extend a label format to support an ODU0 and an ODU4, in many cases, more labels are needed to specify the multiplexing and mapping relation (for example, in a case that a base unit is the ODU0, when the ODU3 is multiplexed to the ODU4, thirty two labels are needed to indicate which 32 TSs of the ODU4 thirty two parts of the ODU3 are mapped to respectively). In a case that the ODUk signal is multiplexed to the ODUj (k<j) signal and multiple labels need to be carried in the label request of the signaling, existing labels is adopted so that signaling overhead in networks is increased, and content expressed by the labels is obscure, so that the expression of TS is difficult to understand and conversion is needed.